1. Field of the Invention
The present invention relates to a device for unfolding a shaped metal article and the method for unfolding the same and, more particularly, to a device for unfolding a shaped metal article having a longitudinal bent or curved portion such that the shaped metal article is unfolded along the bent or curved portion and a method for unfolding the same.
2. Related Art
Aluminum extruded articles have been widely used as various kinds of structural materials because of advantages such as lightness, high productivity and low cost. As a result, it has recently been required that extruded articles having a wide width have been also formed as aluminum extruded articles.
Such an aluminum extruded article is obtained by extruding a billet through a forming slit formed in a die member. To obtain a wide extruded article, a die member, a container and a billet must be large, in accordance with the width of the extruded article. Thus, there will be a certain limitation in enlarging them. It is, therefore, impossible to extrude a wide article having more than a certain width.
To cope with the above-mentioned problems, a method for obtaining a wide structural material has been proposed. The method includes the steps of extruding an aluminum article having a longitudinal bent or curved portion. In the method, the opening angle of the bent or curved portion is gradually enlarged by using a rolling mill.
In the unfolding method mentioned above, however, a roll must be replaced with another roll having a larger opening angle after each unfolding step. Thus, it takes a lot of labor to change rolls. Furthermore, one passing of a roll often may not be enough to unfold the article to a certain opening angle, thus several passings of rolls may be required. Therefore, even in each unfolding step, it takes a lot of time to unfold it. Under the circumstances, the unfolding steps of this method are not performed at a high efficiency.